Anthropic’s Mythos finds no new critical bugs in Zcash

Anthropic’s restricted Mythos model completed a full security audit of the Zcash protocol at Shielded Labs’ request and, as of June 12, 2026, found no additional critical vulnerabilities. Zcash founder Zooko Wilcox-O’Hearn confirmed the result publicly and said the audit covered the protocol state after emergency fixes earlier in June.

Shielded Labs arranged the audit using Mythos, a preview model introduced by Anthropic in April 2026 under Project Glasswing. Access to Mythos is limited to a small group of trusted partners because it can perform autonomous security research and deep code analysis. The audit result was posted on X by Zooko Wilcox-O’Hearn: “At Shielded Labs’s request, they ran a security audit of Zcash with Mythos. It did not find any more serious bugs in the Zcash protocol. Shielded Labs and others are continuing security hardening work. Stay tuned for updates.” The post appeared shortly before reports that Mythos and another advanced model were shut down by the U.S. government that weekend.

The Mythos review followed the disclosure of a critical flaw in the Orchard shielded pool. Security researcher Taylor Hornby, working under contract with Shielded Labs, used a custom AI auditing framework built around Claude Opus 4.8 to identify an under-constrained circuit element in Orchard’s zero-knowledge proof system. The flaw dated to Orchard’s activation in May 2022 and could have allowed undetectable minting inside the privacy pool.

Developers deployed a temporary soft fork on June 2 that disabled Orchard actions. A corrected circuit was activated via the NU6.2 hard fork on June 3, which restored Orchard without a chain split. Public disclosure on June 4 and 5 led to heavy selling that pushed ZEC prices down sharply over 48 hours.

Anthropic’s June 12 audit found no further critical issues beyond the patched Orchard circuit. Shielded Labs and Zcash contributors plan additional security work, including formal verification of the corrected Orchard circuit, more AI-assisted audits, and hires for a Head of Security and a dedicated cryptographer. The team is also preparing the Ironwood upgrade, targeted for late July 2026, which proposes a new shielded pool using the corrected circuit and stricter turnstile accounting to allow independent verification of supply.

On markets, ZEC traded between $411 and $416 on June 13, recovering from intraday lows near $300 on June 5 after the Orchard fix. The token remains below an early-June peak near $624. Market capitalization at current prices is near $6.9 billion to $7.0 billion. Shielded Labs and contributors indicated they will publish further updates as formal verification and the Ironwood proposal progress.